Samsung S6, LG G4, Nexus 6 all have 32 gb as the base model. The Moto x starts at 16 is a fair bit cheaper then the 6S.
And those companies have no choice but to offer something extra that the iPhone does not because they are in desperate straights.
Samsung just starting offering 32GB base THIS YEAR. Their profits are down 70% from its peak. They needed to 'add value' to their phones some how. LG is in deep trouble and may close their phone division soon. Nexus devices sell about 10,000 units a year (exaggeration) and are not mainstream.